Chapter 3 Flashcards
Cell
- Structural and functional unit of life
- Basic unit of life
- Organismal functions depend on individual and collective cell functions
- Biochemical activities
Cell Diversity
- Over 200 different types of human cells
- Types differ in size, shape, sub-cellular components, and functions
General Cell (All Cells)
- All cell have some common structures and functions
- Human cells have three basic parts:
- -Plasma membrane
- -Cytoplasm
- -Nucleus
Plasma Membrane
Flexible outer boundary
-lipid bilayer and proteins constantly changing fluid mosaic
-plays dynamic role in cellular activity
Separates intracellular fluid (ICF) from extracellular (ECF)
–Interstitial fluid (IF)= ECF that surrounds cells
Membrane Lipids
Lipid Bilayer
Phospholipids
- Phosphate heads: polar and hydrophillic (water liking)
- Fatty acid tails: nonpolar and hydrophobic (water fearing)
Membrane Proteins
-Allow communication with environment
-Most specialized membrane functions
2 Types
-Integral Proteins
-Peripheral Proteins
Integral Proteins
Firmly inserted into membrane
- Have both hydrophobic and hydrophilic
- Function as transport proteins (channels and carriers), enzymes, or receptors
Peripheral Proteins
- Loosely attached to integral proteins
- Include filaments on intracellular surface for membrane support
- Function as enzymes
6 Functions of Membrane Proteins
Look at Diagram Cards
- Transport
- Receptors for signal transduction
- Attachment to cytoskeleton and extracellular matrix
- Enzymatic Activity
- Intercellular Joining
- Cell-cell recognition
Glycocalyx
“sugar coverings” at cell surface
- lipids and proteins with attached carbohydrates (sugar groups)
- Every cell has different pattern of sugars
Cell Junctions
2 types
3 subtypes
Some are "free" EX- blood cells, sperm cells Some bond into communities 3 types: -Tight junctions -Desmosomes -Gap junctions
Tight Junctions
Adjacent integral proteins fuse form impermeable junction encircling cell
-prevents movement
Desmosomes
“Rivets” or “spot-welds” that anchor cells together at plaques (thickenings on plasma membrane)
- Linker proteins between cells connect plaques
- Lends stability to cell
- Reduces possibility of tearing
Gap Junctions
Transmembrane proteins form pores that allow small molecules to pass from cell to cell
-for spread of ions, simple sugars, and other small molecules between cardiac or smooth muscle cells
Plasma Membrane
Cells currounded by interstitial fluid (IF)
-contains thousands of substances; amino acids, sugars, fatty acids, vitamins, hormones, salts, waste products
Plasma membrane allows cell to:
-obtain what is needed from IF
-Keep out what it does not need
Membrane Transport
Plasma membranes selectively permeable -some molecules pass through easily; some do not Two ways substances cross membrane -Passive processes -Active processes
Passive Processes
- No cellular energy required
- Substance move down concentration gradient
- Diffusion (2)
- Osmosis
Diffusion
Molecules to move down or with their concentration gradient (speed of movement is determined by molecule size and temperature
Molecule will passively diffuse through membrane if:
-lipid soluble
-small enough to pass through membrane channels
-assisted by carrier molecule
3 Types of Diffusion
Look at Diagram Cards
- Simple Diffusion
- Carrier and Channel Mediated Facilitated Diffusion
- Osmosis
Simple Diffusion
Nonpolar lipid-soluble (hydrophobic) substances diffuse directly through phospholipid bilayer
EX. oxygen, carbon dioxide, fat-soluble vitamins
Carrier-Facilitated Diffusion
Certain lipophobic molecules transported passively by;
-binding to protein carriers
-moving through water-filled channels
Transmembrane integral proteins are carriers
Used when sugars are too large for channels
Channel-Facilitate Diffusion
Watery channels formed by transmembrane proteins
Selectively transport ions or water
Two types:
-Leakage (always open)
-Gateway (controlled by chemical or electrical signals)
Osmosis
Water moves through: -lipid bilayer -specific water channels Occurs when either water or solvent is too high on one side or the other than either: -through impermeable; osmosis occurs until equilibrium reached -through permeable; both solutes and water across membrane until equiilibrium reached
Pressures of Osmosis
Hydrostatic: back pressure of water on membrane
Osmotic: tendency of water to move into cell by osmosis
Importance of Osmosis
Look at Diagram Cards
Causes cells to swell and shrink
change in cell volume disrupts cell function, especially in neurons
Tonicity
Ability of solution to alter cell’s water volume
3 tonics- iso, hyer, hypo
Isotonic
Solution with same non-penetrating solute concentration as cytosol
Hypertonic
Solution with higher non-penetrating solute concentration than than cytosol
Hypotonic
Solution with lower non-penetrating solute concentration than cytocol
Active Processes
2 Types
Requires ATP to move solutes across a plasma membrane because:
-Solute too large for channels
-Solute not lipid soluble
-Solute not able to move down concentration
Two types
-Active Transport
-Vesicular Transport
Active Transport
Requires carrier proteins to move solutes against concentration gradient
Requires energy (ATP)
Energy stored in ionic gradients used indirectly to drive transport of other solutes
Most common is Sodium Potassium Pump
Sodium Potassium Pump
Look at Diagram Cards
Carrier (pump) called Na+-K+ ATPase, located in plasma membranes
Na+ and K+ channels allow slow leakage down concentration gradients
Na+-K+ pumps works as exchanger
-pumps against Na+ and K+
-high intracellular K+ concentration
-high extracellular Na+ concentration
Maintains electrochemical gradients for function of muscle and nerve tissues
Allows all cells to maintain fluid volume
Vesicular Transport
Transport of large particles, macromolecules, and fluids across membrane in membranous sacs called vesicles -Requires energy (ATP) 4 Functions: -Exocytosis -Endocytosis -Transcytosis -Vesicular Trafficking
Endocytosis
Transport into a cell protein-coated vesicles Some pathogens also hijack for transport into cell Once vesicle is inside cell it may: -fuse with lysosome -undergo transcytosis
Exocytosis
Transport out of a cell Usually activated by cell-surface signal or change in membrane voltage Substance enclosed in secretory vesicle Functions: -Hormone secretion -Neurotransmitter release -Mucus secretion -Ejection of wastes
Transcytosis
Transport into, across, and then out of a cell
Vesicular Trafficking
Transport from one area or organelle in cell to another
Resting Membrane Potential (RMP)
- Produced by separation of oppositely charged particles (voltage) across membrane in all cells
- Voltage (electrical potential energy) only at membrane
Electochemical Gradient
electro (charge); chemical (ion concentration)
K+ diffuses out of the cell through K+ leakage channels and so inside cell membrane more negative
K+ attracted back
K+ equalizes across membrane at -90mV when K+ concentration gradient balanced by electrical gradient =RMP
Cytoplasm
Located between the plasma membrane and nucleus
Made of
-Cytosol- water with proteins, salts, and sugars
-Organelles-cell parts with their individual function
Membranous
Rigid with a direct flow
- Mitochondria
- Peroxisomes
- Lysosomes
- Endoplasmic Reticulum
- Golgi Apparatus
Nonmembranous
Free floating
- Cytoskeleton
- Centrioles
- Ribosomes
Mitochondria
- Double membrane structure
- Breaks down food; turns into energy
- Power house
Ribosomes
Makes proteins with RNA Protein Synthesis 2 types: -Free -Membrane-bound
Endoplasmic Reticulum
Two types:
Rough ER
Smooth ER
Rough Endoplasmic Reticulum
Packages proteins, and sends them to the Golgi Apparatus
Smooth Endoplasmic Reticulum
Provides Enzymes to:
- Absorb and transport fats
- Metabolic purposes
- Storage of calcium
Golgi Apparatus
Membranous Sacs
-Modifies, concentrates, and packages proteins and lipids from rough ER
Peroxisomes
Detoxifies harmful or toxic substances
-Neutralize dangerous free radicals
Lysosomes
Destroys cells in injured or non-useful tissue
Contains digestive enzymes
Endomembrane
Inside membrane of the cell Includes: -ER -Golgi Apparatus -Secretory vesicles -lysosomes -nuclear and plasma membranes
Cytoskeleton
Cells skeleton -protects the cell from being squished -structure for the cell Includes -micro-filaments -intermediate filaments -microtubules
Centrosomes and Centrioles
Cell center near nucleus
organizes mitotic spindles
Cilia and Flagella
Cell Extensions
- contains support structure
- moves substances across the cell surface
Microvilli
Cell Extension
-increases surface area for absorption
Nucleus
Nucleus has DNA (blueprint) for making proteins
Responds to signals
Nuclear Envelope
Double Membrane barrier
Protects Nucleus by allowing some substances to pass
Nucleoli
- Within Nucleus
- rRNA synthesis
- Contains DNA coding for rRNA
Chromatin
Threadlike strands of DNA, histone proteins, and RNA
Condenses into barlike bodies called chromosomes when cell starts to divide
Cell Cycle
Changes the formation of the cell until it reproduces.
2 parts
Interphase
Mitotic Phase
Interphase
Cell grows and carries out functions
- Period from cell formation to cell division
- Nuclear material called chromatin
- Adulthood of a cell
Cell Division (Mitotic Phase)
Divides into 2 cells
DNA Replication
Prior to division cell makes copy of DNA
The DNA helix splits and enzymes add nucleotides.
End result: two identical DNA molecules
-Copy given to new cell
-Initial DNA is retained in original cell
Meiosis
Cell divides in half
Ex. Egg and Sperm
Mitosis
Clone
Division of nucleus
Used for growth and tissue repair
Control of Cell Division
“GO” signal
- Cell grows to large so either divide or die
- Need to grow for body to grow
- They want contact so grow and divide so they touch and fill space
Protein Synthesis
DNA is mater blueprint for protein synthesis
Gene-segment of DNA with blueprint for ONE polypeptide
Role of RNA in Protein Synthesis
DNA decoding mechanism and messenger Three types -Messenger RNA (mRNA) -Ribosomal RNA (rRNA) -Transfer RNA (tRNA)
Difference between RNA and DNA
Uracil is substituted for Thymine
Messenger RNA
Carries instructions for building for building polypeptide
- From gene in DNA
- To ribosomes in cytoplasm
Ribosomal RNA
Structural component of ribosomes
-Helps translate message from mRNA
Transfer RNA
- Bind to amino acids
- Begin process of protein synthesis
- Makes proteins
Two Steps for Protein Synthesis
Transcription
Translation
Transcription
Copy Transcription Factors: to make mRNA Loosens DNA in area to be transcribed Makes a template strand RNA polymerase directs this process -Enzyme making it happen
Translation
Decodes
Converts base sequence of nucleic acids into amino acid sequence of proteins
Involves all forms of RNA
Rough ER in Protein Synthesis
Forming protein enters ER
Protein enclosed in vesicle for transport to Golgi Apparatus
Summary: From DNA to Proteins
Complementary base pairing directs transfer of genetic information in DNA into amino acid sequence of protein
- DNA-mRNA
- Complementary base pairing of mRNA with tRNA ensures correct amino acid sequence
- This sequence is identical to DNA sequence except uracil substituted for thymine
Extracellular Materials
Body fluids- interstitial fluid, blood plasma, cerebrospinal fluid
Cellular Secretions- intestinal and gastric fluids, saliva, mucus, and serous fluids
Developmental Aspects of Cells
All cells of body contain same DNA but cells not identical
Chemical signals turn some genes on and others off
Development of specific and distinctive features in cells called Cell Differentiation
Apoptosis
-During development more cells than needed produced
-Eliminated later by programmed cell death
Birth
-Organs well formed and functional before birth
Adulthood
-Cell division to replace short-lived cells and repair wounds
Hyperplasia
Increases cell numbers when needed
Atrophy
decreased size, results from loss of stimulation or use
